Mucopolysaccharide storage diseases or mucopolysaccharidoses (MPS) are lysosomal storage disorders that result from the deficiency of specific lysosomal enzymes. Currently, there are ten types of MPS. They differ in clinical features, accumulated storage materials and deficient enzyme. These storage diseases are characterized by intralysosomal accumulation of mucopolysaccharides, excessive urinary excretion of mucopolysaccharides, progressive mental and physical deterioration, and premature death. Patients are usually born without the visible clinical features of MPS, but develop progressive clinical involvement. Each type of MPS has a specific lysosomal enzyme deficiency with a characteristic degree of organ involvement and rate of deterioration. See Muenzer, Adv. Pediatri. 33:269-302(1986)
Known methods for the quantitative measurement and characterization of MPS are complicated and labor intensive. Generally urine specimens are first concentrated, dialyzed, or the mucopolysaccharide precipitated. The mucopolysaccharide is then identified and quantified by electrophoresis, by determination of uronic acid or by fractionation on a Sephadex column.
A number of screening tests for MPS exist. These tests can be divided into two types: metachromatic reactions of various dyes to glycosaminoglycans; and turbidity or precipitation tests with glycosaminoglycans interacting with acidified albumin solutions of quarternary ammonium compounds. Muenzer, supra. Several of the dye based procedures have been reduced to "spot" tests. These include: Toluidine Blue O Spot Test (Berry Spot Test) [Laboratory Techniques for the Detection of Hereditary Metabolic Disorders, Chp. 5:103-118 (CRC Press); Berry, Clin. Biochem.,20:365-71(1987)]; and Alcian Blue Spot Test [Laboratory Techniques for the Detection of Hereditary Metabolic Disorders supra.]. A qualitative colorimetric method using 1,9-dimethylmethylene blue on liquid urine samples to detect mucopolysaccharidosis in older children exhibiting physical abnormalities associated with MPS is also known. Humbel & Etringer Rev. Roum. Biochem.,11:21-24(1974).
There are a number of drawbacks associated with existing MPS screening tests precluding their use for mass screening of children for MPS in the United States. Many paper spot tests give a high incidence of false-negative results. See Muenzer, supra. In the case of the Berry spot test, a high incidence of false positive is reported and fresh or frozen urine is required. The acid albumin gross turbidity test requires pure liquid urine and is relatively difficult, time consuming and expensive. Specifically, in the case of infants, liquid urine samples are time consuming and inconvenient to obtain and prepare, thus leading to higher costs. Many of the known mucopolysaccharide testing methodologies are inefficient in detecting all mucopolysaccharide disorders. One mucopolysaccharide disorder which is difficult to detect with certain existing methodologies is Morquio syndrome.
Accordingly, there is a need for an improved method to rapidly and accurately detect the presence of all MPS in urine without elaborate sample preparation and need to separate glycosaminoglycan from potentially intereferring substances (e.g., by chromatography) and which is also convenient with respect to the collection and preparation of small samples obtained from newborn infants and young children.